Magnetic properties of LaCo13-based systems

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Abstract
Four polycomponent systems based on LaCo13 have been studied: La(Co1−xFex)13, La(Co1−xAlx)13, La(Co1−x−yFexAly)13, and La0.7Nd0.3(Co0.7Fe0.3)13. These 1:13 systems were studied because of their potential for permanent magnet fabrication. LaCo13 has a high 3d metal content, the highest for any known rare‐earth intermetallic, a 13 kG saturation induction, and a high Tc (1318 K). Unfortunately, it is cubic and lacks anisotropy. The substituted systems were examined as a portion of a program to find LaCo13‐based systems of applications significance. Replacement of Co in LaCo13 by Fe and/or Al leads to a rapid decline in Tc for all systems studied. Replacement of Co by Al results in a decline in moment, whereas replacement by Fe leads to a rise in moment to 2.39μB/3d atom for La(Co0.4Fe0.6)13, as compared to 2.46μB/3d atom for Fe0.7Co0.3. Analysis of the magnetic data shows that vacancies occur in both half‐bands for LaCo13 (4.8 spin up and 3.24 spin down) but in only one half‐band in La(Co1−xAlx)13 for x≥0.2. Nd in these systems carries a moment of 3μB, close to that of the free tripositive ion.